    var gl;
    function initGL(canvas) {
        try {
            gl = canvas.getContext("experimental-webgl");
            gl.viewportWidth = canvas.width;
            gl.viewportHeight = canvas.height;
        } catch (e) {
        }
        if (!gl) {
            alert("webgl不支持");
        }
    }
 
 
    function getShader(gl, id) {
        var shaderScript = document.getElementById(id);
        if (!shaderScript) {
            return null;
        }
 
        var str = "";
        var k = shaderScript.firstChild;
        while (k) {
            if (k.nodeType == 3) {				//3代表文本节点
                str += k.textContent;
            }
            k = k.nextSibling;
        }
 
        var shader;
        if (shaderScript.type == "x-shader/x-fragment") {
            shader = gl.createShader(gl.FRAGMENT_SHADER);
        } else if (shaderScript.type == "x-shader/x-vertex") {
            shader = gl.createShader(gl.VERTEX_SHADER);
        } else {
            return null;
        }
 
        gl.shaderSource(shader, str);
        gl.compileShader(shader);
 
        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(shader));
            return null;
        }
 
        return shader;
    }
 
 
    var shaderProgram;
 	//初始化着色器
    function initShaders() {
		
        var fragmentShader = getShader(gl, "shader-fs");
        var vertexShader = getShader(gl, "shader-vs");
 
        shaderProgram = gl.createProgram();
		//
        gl.attachShader(shaderProgram, vertexShader);
        gl.attachShader(shaderProgram, fragmentShader);
        gl.linkProgram(shaderProgram);
 
        if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
            alert("Could not initialise shaders");
        }
 
        gl.useProgram(shaderProgram);
 		
		
        shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
        gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
 		
		//添加颜色的代码
		shaderProgram.vertexColorAttribute = gl.getAttribLocation(shaderProgram, "aVertexColor"); 
		gl.enableVertexAttribArray(shaderProgram.vertexColorAttribute); 

        shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
        shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
    }
 
 
    var mvMatrix = mat4.create();
    var pMatrix = mat4.create();
 
    function setMatrixUniforms() {
        gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
        gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
    }
 
	
	var triangleVertexPositionBuffer;
 	var triangleVertexColorBuffer;
	//存储颜色信息
  	var squareVertexPositionBuffer;
  	var squareVertexColorBuffer;
 
    function initBuffers() {
        triangleVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
        var vertices = [
             0.0,  1.0,  0.0,
            -1.0, -1.0,  0.0,
             1.0, -1.0,  0.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        triangleVertexPositionBuffer.itemSize = 3;
        triangleVertexPositionBuffer.numItems = 3;
		
		//三角形颜色部分的缓冲区域的数据
		triangleVertexColorBuffer = gl.createBuffer();
	    gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexColorBuffer);
	    var colors = [
	        1.0, 0.0, 0.0, 1.0,
	        0.0, 1.0, 0.0, 1.0,
	        0.0, 0.0, 1.0, 1.0
	    ];
	    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
	    triangleVertexColorBuffer.itemSize = 4;
	    triangleVertexColorBuffer.numItems = 3;
 
 		//矩形的形状数据	
        squareVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
        vertices = [
             1.0,  1.0,  0.0,
            -1.0,  1.0,  0.0,
             1.0, -1.0,  0.0,
            -1.0, -1.0,  0.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        squareVertexPositionBuffer.itemSize = 3;
        squareVertexPositionBuffer.numItems = 4;
		
		//矩形的颜色数据	
		squareVertexColorBuffer = gl.createBuffer();
	    gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexColorBuffer);
	    colors = []
	    for (var i=0; i < 4; i++) {
	      colors = colors.concat([0.5, 0.5, 1.0, 1.0]);
	    }
	    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
	    squareVertexColorBuffer.itemSize = 4;
	    squareVertexColorBuffer.numItems = 4;
    }
 
 
    function drawScene() {
        gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
 		
	/*---视野是45°、canvas的宽高比以及从我们的视点看到的最近距离是0.1个单位，最远距离是100个单位---*/
        mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);
 
        mat4.identity(mvMatrix);
 		
		/*
 		 * 三角形的数据
 		 * 位置，颜色
 		 */
        mat4.translate(mvMatrix, [-1.5, 0.0, -7.0]);
        gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, triangleVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
        
		//绑定颜色的缓冲数据
		gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexColorBuffer);
    	gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, triangleVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);
		
		setMatrixUniforms();
        gl.drawArrays(gl.TRIANGLES, 0, triangleVertexPositionBuffer.numItems);
 
 		/*
 		 * 矩形的数据
 		 * 位置，颜色
 		 */
        mat4.translate(mvMatrix, [3.0, 0.0, 0.0]);
        gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
       
	    gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexColorBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, squareVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);
        
		setMatrixUniforms();
        gl.drawArrays(gl.TRIANGLE_STRIP, 0, squareVertexPositionBuffer.numItems);
    }
 
 //sdfsfsdfs
    function webGLStart() {
        var canvas = document.getElementById("lesson01-canvas");
        initGL(canvas);
        initShaders();
        initBuffers();
 
        gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.enable(gl.DEPTH_TEST);
      
	    drawScene();
    }
